Poly(arylene sulfide) resin, an engineering thermoplastic having outstanding ability to withstand high temperatures and chemical attack, is commercially available. It has been observed that occasionally during the injection molding of certain poly(arylene sulfide) resins mold corrosion occurs. The corrosion has varied from only a slight attack of the mold after extensive molding to very extensive damage after molding for only a short time. Molds of beryllium, copper, and Vega tool steel are most susceptible to such mold corrosion, while molds of stainless steel, such as 303 Stainless, 304 Stainless, and 316 Stainless, and molds with chrome or nickel plating are most resistant to such corrosion. The use of special corrosion-resistant stainless steel mold and chrome or nickel-plated molds can pose an economic burden upon plastic fabricators that do not already have such molds.
It is known to mix certain compounds with the poly(arylene sulfide) resin prior to molding in order to inhibit corrosion of the mold metals, as described in U.S. 4,017,450. In the above referenced patent publication, alkali metal carbonates or hydroxides are disclosed as corrosion inhibitors; and sodium sulfite is disclosed as not inhibiting corrosion.
In a method typical of the above patent, an alkali metal carbonate such as lithium carbonate is incorporated into the poly(arylene sulfide) resin prior to the molding process. However, the development of other additives for combating the corrosion problem would be beneficial for the development of the poly(arylene sulfide) resin technology.
It is an object of my invention to reduce or eliminate mold corrosion resulting when poly(arylene sulfide) resins are molded.
A further object is to provide a poly(arylene sulfide) resin composition that is less likely to cause mold corrosion than prior art poly(arylene sulfide) resin compositions.